HLS simply stops working

[mitchellwrosen]

Hello all, apologies for the low-quality bug report, but I wasn't able to find anything like this in the issue tracker.

Put simply, HLS simply tends to stop working, especially on bigger projects (but why does that matter?)

For example, I'm currently poking around the cabal codebase for the first time. You can follow along by:

• Cloning https://github.com/haskell/cabal
• Building once at the command line for good measure (cabal build cabal-install)
• Opening a file like cabal-install/src/Distribution/Client/Main.hs
• Start to do stuff. Jump around, make type errors, delete an export, just normal coding tasks...

I also have ghcid running in another terminal with ghcid -c 'cabal repl cabal-install', which seems to always report accurate information. That's the easiest way to tell when HLS is wrong - at some point it stops agreeing with ghcid, and it's always wrong when it does.

In a third terminal I have the LSP logs visible at TRACE level. I can see that (when HLS becomes broken) it still seems to be handling many requests. Here's an ugly dump:

[TRACE][2023-12-29 15:56:49] .../lua/vim/lsp.lua:1053	"notification"	"$/progress"	{  token = "2005",  value = {    kind = "begin",    title = "Processing"  }}
[TRACE][2023-12-29 15:56:49] ...lsp/handlers.lua:618	"default_handler"	"$/progress"	{  ctx = '{\n  client_id = 1,\n  method = "$/progress"\n}',  result = {    token = "2005",    value = {      kind = "begin",      title = "Processing"    }  }}
[DEBUG][2023-12-29 15:56:49] .../vim/lsp/rpc.lua:387	"rpc.receive"	{  jsonrpc = "2.0",  method = "$/progress",  params = {    token = "2005",    value = {      kind = "report",      message = "596/599"    }  }}
[TRACE][2023-12-29 15:56:49] .../lua/vim/lsp.lua:1053	"notification"	"$/progress"	{  token = "2005",  value = {    kind = "report",    message = "596/599"  }}
[TRACE][2023-12-29 15:56:49] ...lsp/handlers.lua:618	"default_handler"	"$/progress"	{  ctx = '{\n  client_id = 1,\n  method = "$/progress"\n}',  result = {    token = "2005",    value = {      kind = "report",      message = "596/599"    }  }}
[DEBUG][2023-12-29 15:56:49] .../lua/vim/lsp.lua:1392	"LSP[haskell]"	"client.request"	1	"textDocument/codeLens"	{  textDocument = {    uri = "file:///home/mitchell/code/forks/cabal/cabal-install/src/Distribution/Client/Main.hs"  }}	<function 1>	2
[DEBUG][2023-12-29 15:56:49] .../vim/lsp/rpc.lua:284	"rpc.send"	{  id = 419,  jsonrpc = "2.0",  method = "textDocument/codeLens",  params = {    textDocument = {      uri = "file:///home/mitchell/code/forks/cabal/cabal-install/src/Distribution/Client/Main.hs"    }  }}
[DEBUG][2023-12-29 15:56:49] .../vim/lsp/rpc.lua:387	"rpc.receive"	{  jsonrpc = "2.0",  method = "$/progress",  params = {    token = "2005",    value = {      kind = "report",      message = "325/599"    }  }}
[TRACE][2023-12-29 15:56:49] .../lua/vim/lsp.lua:1053	"notification"	"$/progress"	{  token = "2005",  value = {    kind = "report",    message = "325/599"  }}
[TRACE][2023-12-29 15:56:49] ...lsp/handlers.lua:618	"default_handler"	"$/progress"	{  ctx = '{\n  client_id = 1,\n  method = "$/progress"\n}',  result = {    token = "2005",    value = {      kind = "report",      message = "325/599"    }  }}
[DEBUG][2023-12-29 15:56:49] .../vim/lsp/rpc.lua:387	"rpc.receive"	{  jsonrpc = "2.0",  method = "$/progress",  params = {    token = "2005",    value = {      kind = "report",      message = "322/599"    }  }}
[TRACE][2023-12-29 15:56:49] .../lua/vim/lsp.lua:1053	"notification"	"$/progress"	{  token = "2005",  value = {    kind = "report",    message = "322/599"  }}
[TRACE][2023-12-29 15:56:49] ...lsp/handlers.lua:618	"default_handler"	"$/progress"	{  ctx = '{\n  client_id = 1,\n  method = "$/progress"\n}',  result = {    token = "2005",    value = {      kind = "report",      message = "322/599"    }  }}
[DEBUG][2023-12-29 15:56:49] .../vim/lsp/rpc.lua:387	"rpc.receive"	{  id = 419,  jsonrpc = "2.0",  result = {}}
[DEBUG][2023-12-29 15:56:49] .../vim/lsp/rpc.lua:387	"rpc.receive"	{  jsonrpc = "2.0",  method = "$/progress",  params = {    token = "2005",    value = {      kind = "end"    }  }}
[TRACE][2023-12-29 15:56:49] .../lua/vim/lsp.lua:1053	"notification"	"$/progress"	{  token = "2005",  value = {    kind = "end"  }}
[TRACE][2023-12-29 15:56:49] ...lsp/handlers.lua:618	"default_handler"	"$/progress"	{  ctx = '{\n  client_id = 1,\n  method = "$/progress"\n}',  result = {    token = "2005",    value = {      kind = "end"    }  }}

But within the editor, I'm no longer getting any feedback whatsoever. I just have to restart HLS, and then it works again.

Again, apologies for the relatively low-quality bug report. I just wanted to make sure that this issue is known. I'd be happy to jump on a call to assist in collecting more information, if that would be helpful. It's easy for me to trigger this behavior on my end. Thanks!

[fendor]

I noticed this for the cabal codebase as well. I think it is a symptom of lacking multiple home unit support which requires cabal 3.12 and HLS head to work properly.

[michaelpj]

Is this reproducible with the latest HLS and cabal?

[mitchellwrosen]

Yes, it is, and I have a slightly more detailed repro this time around:

• (as above) build with cabal build at the command-line just for good measure
• open cabal-install/src/Distribution/Client/Main.hs and let hls settle ("setting up" followed by "indexing")
• open Cabal/src/Distribution/Simple/Command.hs
• go back to the first file, hls now only provides syntax errors

[fendor]

That's exactly the kind of issues that should be fixed by multi-repl: True, once cabal-3.12 is released.

Ill try to use it.

[fendor]

Works with the pre-release and HLS 2.8.0.0:

Note the hover on the right.

[michaelpj]

Okay, tentatively closing, then.